The specific aim of this study is to quantify alterations in microvascular permeability of normal and neoplastic tissue by direct in vivo measurement of the extravasation of fluorescein-tagged dextran (molecular weight = 150,000) following local or systemic administration of vasoactive agents. These agents include amines (prostaglandins and leukotrienes), polypeptides (angiotensin, bradykinin, and vasopressin), catecholamines (epinephrine and norepinephrine) and glucose. Dose-response curves will be constructed for every agent. Experimental methods will involve growing normal (mature granulation) and neoplastic VX2 carcinoma) tissues in a transparent rabbit ear chamber prepared routinely in our laboratory. Once the tissue prepration is mature, fluorescein isothiocyanate (FITC)-tagged dextran molecule (molecular weight of 150,000) will be injected into the animal's circulation. Fifteen minutes later, a vasoactive agent will be administered locally or systemically. Resulting extravasation of FITC-dextran will be monitored and video recorded for up to three hours using an intravital fluorescene microscopy technique developed and tested in our laboratory. Stemic blood pressure of animals will be monitored in each experiment. In a limited number of experiments, microvascular pressure will be measured by opening the chamber carefully and inserting micropipette in desired blood vessels. The spatial and temporal concentration data will be used to calculate the interstitial diffusion coefficient and effective microvascular permeability using previously developed mathematical models. Theoretical work will involve development of mathematical models to quantify changes in microvascular transport and endothelial damages. Single capillary models will be extended to multiple capillaries, wherein the morphological and transport chracteristics of each capillary can be different. It is hoped that the results of this investigation using vasoactive agents as a probe will increase our fundamental understanding of the structural and functional differences between normal and neoplastic microcirculation and will aid in improving the current methods of cancer detection and treatment. (4)